The present invention relates to a method of preparing a negative active material for a rechargeable lithium battery and a rechargeable lithium battery.
A battery is a device for generating electrical power by using materials which can react electrochemically in positive and negative electrodes. As a representative example of a battery, there is a rechargeable lithium battery that generates electrical energy by the change in chemical potential when lithium ions are intercalated/deintercalated in positive and negative electrodes.
The rechargeable lithium battery can be prepared by using materials which can intercalate/deintercalate lithium ions reversibly as a positive active material and a negative active material, and by filling the space between the positive electrode and the negative electrode with an organic electrolyte or a polymeric electrolyte.
Lithium-metal complex compounds have been used as the positive active material of a rechargeable lithium battery, for example, the lithium-metal complex oxides such as LiCoO2, LiMn2O4, LiNiO2, LiNi1-xCoxO2(0<x<1), LiMnO2, and the like.
Various types of carbon-based materials which can intercalate/deintercalate lithium, such as artificial graphite, natural graphite, hard carbon, and the like, have been used as the negative active material of the rechargeable lithium battery. Among the carbon-based materials, graphite has been the most widely used as the negative active material. Graphite provides an advantage in energy density of the lithium battery and secures long life of the rechargeable lithium battery with its excellent reversibility. This is because negative active materials comprised of graphite have a low discharge voltage of −0.2V, wherein negative active materials comprised of lithium have a low discharge voltage of 3.6V. However, the graphite active material has a disadvantage of low capacity in view of energy density per unit volume of the electrode because graphite has a very low density of about 1.6 g/cc when prepared into an electrode.
Recently, there have been ongoing studies to find alternative high capacity negative active materials other than the widely used graphite.